Disk drives are widely used for data storage. A typical disk drive includes one or more rotatable disks and an actuator arm. A suspension attached to the actuator arm supports a magnetic head which reads and writes data to selected tracks on the disk surface.
A pivot bearing supports the actuator arm, enabling the arm to pivot the magnetic head between tracks. Precise positioning of the magnetic head at a particular track must be accomplished if the stored data on that track is to be read. Accordingly, it is critical that the pivot bearing minimize play in the actuator arm.
Pivot bearings are typically press-fit into an actuator arm bearing housing to minimize actuator arm play. For example, U.S. Pat. No. 5,041,934 to Stefansky describes a typical actuator assembly with a press-fit pivot bearing. The bearing 162 is cylindrical, having a recessed middle portion, a first end and a second end. The ends have equal diameters, which press-fit into the actuator arm bearing housing. A drawback of the bearing design employed by Stefansky is that in order to press-fit both ends of the bearing into the actuator arm, the first bearing end presses fully through the full length of the bore. Pressing the first end deforms (i.e. widens) the bore. When the second bearing end enters the pre-widened bore, the resulting press-fit is looser at the second bearing end than the press-fit of the first bearing end. Bearing misalignment may adversely affect vibration characteristics of the actuator arm and the disk drive. In extreme cases, actuator arm vibration may shift the read/write head from a particular track. This can delay or inhibit reading of data from the track.
U.S. Pat. No. 5,539,597 to Blanks describes a pivot assembly for an actuator arm having two sets of cylindrical-shaped bearings. The Blanks bearing housing provides two discrete shoulders 38 and 40 to enable each bearing to seat during a press-fit. Independently seating bearings reduces the pre-widened bore problem identified with respect to Stefansky. Increasing the number of bearings required by the actuator arm, however, increases the probability of misalignment of any one bearing. Installation of multiple bearings is typically more complicated than single bearing installation. A better way of assuring actuator arm alignment is desired.